Preheat your oven to 350°F (175°C). Grab a standard-sized loaf pan (about 9x5 inches) and grease it well, or line it with parchment paper for easy removal.
In a medium bowl, whisk together your dry ingredients: the almond flour, coconut flour, baking powder, cinnamon, xanthan gum, and sea salt. Give it a good mix to make sure everything is evenly distributed.
In a separate, larger bowl (or the bowl of your stand mixer), cream together the softened butter and the Besti Monk Fruit Allulose Blend until the mixture is light and fluffy. You can use an electric mixer for this, or just a good old whisk and some elbow grease!
Beat in the eggs one at a time, making sure each one is fully incorporated before adding the next. Scrape down the sides of the bowl as needed.
Now, pour in the room temperature almond milk and the banana extract. Mix until just combined. The mixture might look a little separated or curdled at this point, but don't panic! That's okay.
Gradually add the dry ingredients from the medium bowl to the wet ingredients in the larger bowl. Mix on low speed or by hand with a spatula until just combined. Be careful not to overmix!
If you're using walnuts, gently fold in about 3/4 cup of the chopped nuts into the batter. Save the rest for the topping.
Pour the batter evenly into your prepared loaf pan. Sprinkle the remaining 1/4 cup of chopped walnuts (if using) over the top of the batter.
Bake for 45-60 minutes, or until the bread is golden brown on top and a toothpick inserted into the center comes out clean. Keep an eye on it towards the end of the baking time. If the top starts browning too quickly, you can loosely tent it with foil.
Once baked, remove the loaf from the oven and let it cool in the pan for about 10-15 minutes before carefully removing it and transferring it to a wire rack to cool completely. Letting it cool properly helps it set and prevents it from falling apart.
Slice and enjoy! It's absolutely divine warm with a smear of butter or cream cheese!